A recent study published in the Journal of Cataract & Refractive Surgery evaluated the association between keratoconus (KC) and autism spectrum disorder (ASD) in the Norwegian population.
Give me some background.
KC is a multifactorial, bilateral ectatic corneal disease with an estimated prevalence of 0.2-1.2% in the general population.
A previous national registry study from Norway found that 73% of the people diagnosed with KC were men.
- Note: This was of interest to the study authors because ASD is another condition that has been shown to be more prevalent in men.
To tie it all together: Studies have reported a high prevalence of astigmatism among autistic people— and due to the fact that ASD is also predominant in men, the research team hypothesized that autistic individuals may have an increased risk of KC.
Let’s get back to the study.
In this nationwide cross-sectional epidemiological study, investigators analyzed data from the Norwegian Patient Registry (NPR), which provides information from all publicly-funded specialist care.
Using this data, the research team estimated the KC prevalence among autistic people from the total number of individuals with KC from 2010-2019.
- Then: They compared this number to the KC prevalence in the general population of Norway during the same time period.
And their findings?
The population-based sample in Norway identified 23,763 autistic individuals (0.5% of the population). Of these, 115 (0.5%) had a KC diagnosis.
The average age at KC diagnosis in individuals with ASD was 27.3 years, and 83.5% of those diagnosed with both ASD and KC were men.
During the same time period, the prevalence of KC in the general population was 0.2%, resulting in an odds ratio of 2.5 (95% confidence interval: 2.0-3.0).
Expert opinion?
Studies have suggested that eye rubbing is a risk factor for KC and contributes to the development of the disease.
- Additionally: Eye rubbing, a form of repetitive behavior, is also commonly observed in children with ASD.
The study authors explained: “If autistic individuals truly have a higher prevalence of both KC and eye rubbing, one could ask:
- If it is the act of eye rubbing itself that leads to the increased risk of KC
- If it is related to something inherent about this population that makes them more susceptible to the condition
- Possibly a combination of the two”
Anything else?
Note: A study on KC prevalence in university students and faculty members found that 78.6% of those with KC were unaware of their disease.
“Considering this, along with the communication often associated with ASD, one could argue that routine follow-up for ocular manifestations, such as KC, is particularly important in this population, in order to prevent deterioration of vision that may be preventable,” they added.
Limitations?
These included:
- Reliance on a register, which could potentially create selection bias where some groups can be underrepresented because it excludes individuals who do not seek help
- Variations in diagnostic practices and equipment may affect the accuracy and consistency of the KC diagnosis, potentially leading to information bias
- The diagnosis of KC and ASD were not standardized because the coding was assigned by various clinicians
- The absence of data from privately financed healthcare
- Some KC cases are not likely discerned by optometrists, and thus were not referred to an ophthalmologist or included in the NPR
Take home.
These findings suggest that autistic individuals have significantly higher prevalence of KC compared to the general population of Norway.
Meaning: Clinicians should have increased awareness of KC and low threshold for corneal tomography in autistic individuals.